Apparatus and method for adapting multiple operating mode monitor

ABSTRACT

An adapter for a multiple operating mode monitor automatically controls the horizontal and vertical deflection circuits of the monitor cathode ray tube depending upon the characteristics of the video source to which the monitor is connected. The adapter has a digital memory for storing sets of monitor operating parameters for each of a plurality of predetermined operating modes at selectively addressable locations. A processor evaluates horizontal and vertical synchronizing signals from a video source to which the monitor is connected to identify one of the plurality of predetermined operating modes corresponding to the synchronizing signals. The operating mode may be evaluated and identified by measuring the period of the horizontal and vertical synchronizing signals form the video source. The memory location corresponding to the identified mode of operation is selectively addressed, the selected set of operating parameters, which may be in parallel format, being available as an output to a plurality of dynamic digital to analog converters. The digital to analog converters, which may be synchronized with the vertical frequency, provide analog control signals for the horizontal and vertical deflection circuits. The horizontal and vertical deflection circuits are adjusted responsive to the analog control signals to correspond to the selected set of operating parameters. The operating parameters may include horizontal and vertical frequency, horizontal and vertical amplitude, horizontal and vertical deflection phase position, brightness and contrast.

The variety of different personal computers and monitors has resulted inthe creation of many different operating modes for the input signalsrequired by the monitors. Until now, it has been impossible to operateany given monitor with another personal computer without specialadaptation. Rather, a specific adapter board had to be used for eachoperating mode. The operating modes can be distinguished mainly on thebasis of their line frequency, picture frequency, the number of scanlines and the horizontal and vertical amplitude, as well as theirformats usable within the screen format.

It is an aspect of the invention to provide a method by means of whichthe signal of the personal computer designated for the monitor may beevaluated for characteristics specific for the computer's operatingmode, to initiate an automatic adaptation of the monitor to theidentified operating mode.

This aspect of the invention may be achieved by a method for adapting amultiple mode monitor to a plurality of video sources having differentoperating parameters. A first step may be storing sets of monitoroperating parameters for each of a plurality of operating modes atselectively addressable locations. A second step may be evaluatinghorizontal and vertical synchronizing signals from a video source towhich the monitor is connected to identify one of a plurality ofpredetermined operating modes corresponding to the synchronizingsignals. A third step may be selectively addressing the set of operatingparameters corresponding to the identified operating mode. A final stepmay be adjusting operation of the monitor, for example, the horizontaland vertical deflection circuits, to correspond to the selected set ofoperating parameters. The synchronizing signals may be evaluated bymeasuring the respected periods of the synchronizing signals. A timebase may be derived from the vertical synchronizing signals formeasuring the period of the horizontal synchronizing signals. Theoperating parameters may be stored as digital data and converted toanalog control signals by dynamic digital-to-analog conversion. Thedynamic digital-to-analog conversion may be synchronized with thevertical frequency. The number of steps in the digital-to-analogconversion for each period of the vertical synchronizing signal may beheld to a constant number of steps.

In accordance with an inventive aspect of the invention, the ratings oroperating parameters of frequently occurring operating modes are storedin a memory. This may be done, for example, by prior adjustment withtest signals. After the termination of testing, the parameters soobtained may be written into the memory designated for this purpose, forexample, a read only memory. The ratings are stored under addressesspecific for the operating modes. After selection of one of theaddresses, all required ratings will be present at the output of thememory. If it is possible to definitely deduce the operating mode byevaluation of the horizontal and vertical synchronizing signals of thepersonal computer, the address allocated to this operating mode can becalled, and the operating mode can be set. The operating mode is set byfeeding signals from the memory output to the horizontal and verticalscanning stage of the monitor. This stage includes the horizontal andvertical deflection circuits. As the setting occurs immediately afterthe reception of horizontal and vertical synchronizing signals, the timerequired for setting can barely be noticed by the user. It is evenpossible to switch a monitor in operating to another personal computer,without the need to consider whether the other personal computer usesthe same or another operating mode. The number of possible operatingmodes which can be set automatically under the invention is unlimited inprinciple. In practice, however, it is dependent on the size of thememory which is used for storing the parameters or ratings.

In accordance with another aspect of the invention, it is also possibleto distinguish those operating modes that coincide in one of the valuesby evaluating both the horizontal and the vertical synchronizationsignals, as done in a further development. In one embodiment thedetermination of the period or duration of the horizontal synchronizingsignals may be determined by measuring several periods and dividing bythe number of synchronizing signals. In this way it is possible toobtain a high degree of measuring accuracy in spite of the clock pulsefrequency of the microprocessor being within the same range as thehorizontal frequency, without the need for additional circuits.

It is especially advantageous to run the control signals for thehorizontal and vertical scanning stages of the monitor through dynamicdigital-to-analog converters because triggering via the serial output ofa microprocessor becomes possible. The disadvantage normally entailed inthese kind of digital-to-analog converters, namely that deviations ofthe horizontal or vertical frequency from the conversion frequency causea flicker or an unevenly bright picture, can be overcome. In accordancewith yet another aspect of the invention, the dynamic digital-to-analogconverters are synchronized with the vertical frequency, for example, byobserving a constant number of steps in every period.

A video test signal is advantageously used to make it possible at thefirst setting of ratings, or at putting the multiple operating modemonitor into use, to obtain an exact setting which will not have to belater corrected. Thus, it is certain that the whole dynamic function ofthe analog-to-digital converters are utilized. The video test signal ismainly used for adjustment of the amplitude and phase of the horizontaland vertical deflection. A test signal of a simple design is sufficientfor this purpose. It is only important that the respective markings arecreated at exactly defined times so that a correlation between the testsignals visible on the screen and the reference of the ratings isestablished.

It is particularly simple to create test signals in the form of barswhich mark the horizontal and vertical borders of the usable screenarea. Additional bars may be created for the adjustment of the geometry.In order to accomplish this by a microprocessor which is also used forother purposes, the video test signals are created as a serial data flowand drawn from a serial output of a microprocessor. The data flow may begenerated by a shift register which has previously been loaded in asubroutine according to the designated picture pattern and is triggeredafter interruption of a main program. The normal program can then becontinued during the serial data flow. It is sufficient to trigger thevideo signal anew in a subroutine loop periodically after eachhorizontal synchronizing signal.

It is still another aspect of the invention to provide an apparatusadapting a multiple operating mode monitor to a personal computer.

In this respect, it is also an aspect of the invention to automaticallyset one of several recurrent operating modes by evaluating thecharacteristics of the signal coming from a personal computer designatedfor the monitor.

In accordance with this aspect of the invention, an adapter forcontrolling a multiple operating mode monitor may comprise a memory forstoring sets of monitor operating parameters for each of a plurality ofoperating modes at selectively addressable locations. A processor may beprovided for evaluating horizontal and vertical synchronizing signalsfrom a video source to which the monitor is connected to identify one ofa plurality of predetermined operating modes corresponding to thesynchronizing signals. The memory location corresponding to theidentified mode of operation may be selectively addressed, the selectedset of operating parameters being available as an output to a pluralityof dynamic digital-to-analog converters. The digital-to-analogconverters, which may be synchronized with the vertical frequency,provide analog control signals for the horizontal and verticaldeflection circuits. The horizontal and vertical deflection circuits areadjusted responsive to the analog control signals to correspond to theselected set of operating parameters. The adapter may be incorporatedinto new multiple operating mode monitors, or may be adapted forretrofitting existing multiple operating mode monitors.

The microprocessor and the memory make it possible to store allnecessary parameters for the possible operating modes and are capable ofevaluating the horizontal and vertical synchronizing signals of thepersonal computer as criteria for determining which parameters are to beset. The values for the duration or period of the horizontal andvertical synchronizing signals are stored in a memory and these valuesare compared with the measured values. In case of a match, storagelocations can be addressed which contain the preset parameters. When thestorage location is addressed, the preset parameters are triggered intotransmitting control signals for setting the parameters in thehorizontal and vertical scanning stages of the monitor.

The dynamic digital-to-analog converters which are used according to afurther aspect of the invention for conversion of the digital signalsinto analog signals can be designed very simply and can be connectedsignal-wise particularly well to microprocessors with a usual singleoutput.

Further aspects of the invention will be apparent from the followingdescription and drawings which illustrate an embodiment of theinvention.

FIG. 1 is a flow chart illustrating a method for operating a monitorwith multiple operating modes.

FIG. 2 is a block schematic diagram of a circuit for operating a monitorwith multiple operating modes.

The process shown in FIG. 1 commences at Start 1. After the Start 1, adecision is made in 2 as to whether a signal is being fed to the TTL, ordigital, input. If the answer is yes, the process is continued at 3 bymeasuring the horizontal and the vertical frequency. If the answer isno, the active input is switched over at 4 from the TTL input to theanalog input. A check is made at 5 as to whether the signal is nowpresent at the analog input. If the answer is yes, the next step in theprocess is number 3; if the answer is no, the active input is changed at6 back over to the TTL input from the analog input and a jump is madeback to the decision at 2.

After measuring the frequencies at 3, the frequency is displayed at 7and compared to stored ratings or parameters at 8. Step 9 asks whether apair of ratings has been recognized. If the answer is yes, therespective memories are addressed and the memory contents are read outat 10. After a digital-to-analog conversion of the stored data done at11, the triggering of the horizontal and vertical stages is done byrespective analog corrective signals at 12.

After conclusion of this process step, a scanning 13 is used to checkwhether the operating signal has been altered. If the answer is yes, theprocess jumps back to Start 1 and the process steps as described aboveare executed again. If the operating signal has not been altered, thekeyboard is then read at 14 to consider desired values for brightness,contrast, horizontal or vertical amplitude and horizontal or verticalposition. Thereafter, step 15 asks whether a video signal is desired. Ifthe answer is yes, a video test routing is called at 16 and a jump ismade back to 14 to alter the respective values through the keyboard. Ifno video test signal is desired, a jump is made back to 13.

If at 9 a pair of ratings is not recognized, the process branches to 17,which asks whether the new pair of horizontal and vertical frequencyshould be stored. If the answer is yes, the storing and preparation ofthe storage locations for the scanning stage and the ratings is done at18. If the answer is no, a jump is made to 13.

An apparatus according to the invention is shown in FIG. 2. Personalcomputer 20 is equipped with a TTL video adapter board, and personalcomputer 21 is equipped with an analog video adapter board. The digitalmonitor signal from personal computer 20 is fed to input 22 atchange-over switch 24. The analog monitor signal from personal computer21 is fed to input 23 of change over switch 23. The signals are fed fromchange-over switch 24 and a signal conversion circuit to a microcomputer25. Video parts of the signal are also directly fed to a monitor 27 fedvia a video stage 26. A control line 38 runs back from the microcomputer25 to the change-over switch 24, which makes it possible toalternatively connect digital TTL-signals and analog signals to themicrocomputer 25 and the monitor 27. The microcomputer 25 comprises acentral processing unit CPU 28, a read only memory ROM 29 and a randomaccess memory RAM 30. Storage locations are available in RAM 30 forseveral operating modes. These storage locations can be addressed, andthe contents of the memory can then be transmitted to thedigital-to-analog converters, 31 through 37. The digital-to-analogconverters 31 through 37 transmit control signals to a video stage 26 ora horizontal scanning stage 39 or, respectively, a vertical scanningstage 40. A display unit 41 and an input unit 42 are also connected tothe microcomputer 25. The input unit 42 enables the horizontal andvertical amplitude, the horizontal and vertical position as well asbrightness and contrast to be set. Furthermore, a video test signal canbe activated. If storage of a pair of frequency values is desired, thiscan be stored in the RAM 30 through a storage a storage command key. Apersonal computer with the respective operating mode can then, on thebasis of the pair of values of horizontal and vertical frequency,automatically be adapted to the monitor with respect to the otheroperating modes.

The signals present at the input of the microcomputer 25 designated forthe monitor are evaluated by the microcomputer as to the duration of theperiod of their horizontal and vertical synchronizing signals. This pairof values is compared to pairs of values stored in the RAM 30. In caseof recognition of matching pairs of values, the appropriate storagelocations are addressed, and subsequently read out. The stored valuesrepresenting the respective ratings or parameters are then converted torespective control signals by the digital-to-analog converter 31.Horizontal and vertical frequency is determined by the control signalsof digital-to-analog converters 32 and 35 respectively. Horizontal andvertical amplitude is determined by the control signals ofdigital-to-analog converters 33 and 36, respectively. Finally the phaseposition of the horizontal and vertical deflection is determined by thecontrol signals of digital-to-analog converters 34 and 37, respectively.

I claim:
 1. An adapter for controlling a multiple operating modemonitor, comprising:a memory for storing sets of monitor operatingparameters for each of a plurality of operating modes at selectivelyaddressable locations; processing means for evaluating horizontal andvertical synchronizing signals from a video source to which the monitoris connected to identify one of a plurality of predetermined operatingmodes corresponding to the synchronizing signals; means for selectivelyaddressing the set of operating parameters corresponding to theidentified operating mode; and, means for adjusting operation of themonitor to correspond to the selected set of operating parameters. 2.The adapter of claim 1, further comprising a plurality of dynamic analogto digital converters coupled between the adjusting means and horizontaland vertical scanning circuits of the monitor.
 3. The adapter of claim1, wherein each set of the operating parameters comprises informationidentifying horizontal frequency, vertical frequency, horizontalamplitude and vertical amplitude.
 4. The adapter of claim 3, whereineach set of the operating parameters further comprises informationidentifying horizontal deflection phase position, vertical deflectionphase position, brightness and contrast.
 5. The adapter of claim 1,wherein the evaluating means and the selecting means are embodied in amicroprocessor.
 6. The adapter of claim 1, further comprising a furthermemory for storing evaluation criteria for comparison with thesynchronizing signals.
 7. The adapter of claim 1, further comprisingcontrol means for loading the memory with the sets of operatingparameters.
 8. The adapter of claim 1, further comprising:a change overswitch having respective inputs for connecting digital and analog videosources to the monitor; and, means for determining which of the inputsis connected to a video source.
 9. The adapter of claim 2, furthercomprising means for synchronizing operation of the digital to analogconverters with the vertical frequency.
 10. A multiple operating modemonitor, comprising:a cathode ray tube; horizontal and verticaldeflection circuits coupled to the cathode ray tube; a digital memoryfor storing sets of monitor operating parameters for each of a pluralityof operating modes at selectively addressable locations; processingmeans for evaluating horizontal and vertical synchronizing signals froma video source to which the monitor is connected to identify one of aplurality of predetermined operating modes corresponding to thesynchronizing signals; means for selectively addressing and outputtingthe set of operating parameters corresponding to the identifiedoperating mode; and, plurality of dynamic digital to analog converterscoupled to the addressing and outputting means for converting theoperating parameters into analog control signals for the horizontal andvertical deflection circuits; and, means for adjusting operation of thedeflection circuits responsive to the analog control signals tocorrespond to the selected set of operating parameters.
 11. The monitorof claim 10, further comprising means for synchronizing operation of thedigital to analog converters with the vertical frequency.
 12. Themonitor of claim 10, wherein each set of the operating parameterscomprises information identifying horizontal and vertical frequency,horizontal and vertical amplitude, horizontal and vertical deflectionphase position, brightness and contrast.
 13. The monitor of claim 10,further comprising:a change over switch having respective inputs forconnecting digital and analog video sources to the monitor; and, meansfor determining which of the inputs is connected to a video source. 14.The monitor of claim 10, further comprising control means for loadingthe memory with the sets of operating parameters.
 15. A method foradapting a multiple mode monitor to a plurality of video sources havingdifferent operating parameters, comprising the steps of:storing sets ofmonitor operating parameters for each of a plurality of operating modesat selectively addressable locations; evaluating horizontal and verticalsynchronizing signals from a video source to which the monitor isconnected to identify one of a plurality of predetermined operatingmodes corresponding to the synchronizing signals; selectively addressingthe set of operating parameters corresponding to the identifiedoperating mode; and, adjusting operation of the monitor to correspond tothe selected set of operating parameters.
 16. The method of claim 15,comprising the step of evaluating the synchronizing signals by measuringthe respective periods of the synchronizing signals.
 17. The method ofclaim 16, comprising the step of measuring several periods of thehorizontal synchronizing signal and dividing by the number of horizontalsynchronizing signals detected.
 18. The method of claim 16, comprisingthe step of deriving a time base from the vertical synchronizing signalsfor measuring the period of the horizontal synchronizing signals. 19.The method of claim 15, comprising the steps of:storing the operatingparameters as digital data; dynamically converting the digital data toanalog control signals; and, synchronizing the dynamic digital to analogconversion with the vertical frequency.
 20. The method of claim 19,further comprising the step of maintaining a constant number of steps inthe digital to analog conversion for each period of the verticalsynchronizing signal.
 21. The method of claim 19, further comprising thestep of calibrating the monitor by generating a video test pattern. 22.The method of claim 21, comprising the step of triggering the video testpattern after each horizontal synchronizing signal.
 23. The method ofclaim 21, comprising the step of generating the video test pattern froma serial data stream.
 24. The method of claim 19, comprising the step ofstoring an operating parameter for horizontal and vertical frequency,horizontal and vertical amplitude, horizontal and vertical deflectionphase position, brightness and contrast.